Look at MCU as a whole. People don't just go see one character's movies, they see them all. They built up to Avengers and now they have Infinity War coming so people will check for Thor just to see how it connects. While the movies were weak people have seen the character enough to like him. If Marvel had a bad movie they always rebounded with a Winter Soldier or Guardians.
BvS
Suicide Squad
DCEU got off on the wrong foot. Wonder Woman isn't enough to get the audience to trust them. Justice League is on the way and we don't even know most of the team. Aquaman, Cyborg, and Flash are new. This new Batman didn't have his own movie and people had issues with him killing in BvS. Wonder Woman is only 1 movie in and they were pushing her hard in the trailer. They "killed" Superman
.
Afleck stepped down as director and had people thinking he'd leave Batman altogether. Snyder had to walk away for personal reasons. There's conflict with WB. They're not running a tight ship.